The correct answer is A because it represents a lagging indicator , not a leading metric.

CCPS distinguishes between leading and lagging indicators in process safety. Leading indicators are proactive measures that monitor system performance and help prevent incidents before they occur. In contrast, lagging indicators measure outcomes after an event has already happened , such as incidents, injuries, or losses.

Option A (number of actual process safety incidents in the past year) is clearly a lagging metric , as it reflects failures that have already occurred. While useful for tracking historical performance, it does not help proactively improve emergency preparedness.

Options B, C, and D are all leading indicators . The number of trained responders (B) reflects preparedness and capability. The number of plan revisions (C) indicates continuous improvement and updating of emergency procedures. The number of realistic drills (D) demonstrates active testing and validation of emergency response systems.

CCPS emphasizes that effective emergency management relies heavily on leading indicators , as they provide early insight into readiness and allow organizations to address gaps before an actual emergency occurs.